The present application relates generally to the field of optical sensors and more specifically to fiber optic sensor interrogation systems.
Aerospace vehicles and systems are typically equipped with instruments that monitor the status and/or condition of various systems by acquiring, exchanging and analyzing data, and the communication networks in such arrangements must be robust enough to withstand repetitive and potentially destructive forces and conditions, while transmitting and processing the data collected.
In recent years, there has been a trend to use optical apparatus in lieu of electrical or mechanical devices for the purpose of monitoring the status and/or condition of such systems. Optical interrogation systems are integral components in status and/or condition monitoring systems used in chemical, biological, temperature and pressure sensing environments. Optical sensing techniques are highly desirable for aerospace applications due to the lighter weight and EMI continuity, but to date such sensor systems have proven too costly or complicated to deploy.
One potential drawback to current optical sensing techniques is that current optical based sensing systems tend to make heavy use of lasers. The monochromatic light and ability to couple into single mode fiber makes the pairing a good solution for many applications, but has resulted in difficulties for aerospace use. The sensitivity of laser based systems, and the declining use of single mode fiber has led the inventors to look into other methods of optical sensor interrogation. Communication based systems are increasingly using a low cost laser type called Vertical Cavity Surface Emitting Laser (VCSEL). Such devices in the past had been relatively failure-prone and prone to damage when used in adverse environments, such as areas of high humidity. While costs for such devices are dropping, and reliability is increasing, these devices still are not clearly desirable for use in an aerospace environment, in particular when looking at new technology sensor solutions such as photonic crystal sensors.
Another potential drawback is the traditional approach to sensing within sensor systems. Various solutions have been proposed and tried, including Fiber Bragg Grating (FBG) type sensor systems, fiber optic path sensing, piezoelectric transducers, comparative vacuum monitors, strain gauge based systems, ultrasonic systems, and visual indicators, but each has challenges.